cxlviii BRITISH GRAPTOLITES. 



in these beds for the first time the existence of five distinct 



1901. 



zones : 



Tornquist, . . 



" Graptolites of the (") Zone of Tetra graptus phyllograptoides. 



Lower Zones of the (0 z °ne of Didymograptus balticus. 



Scanian and Vestro- (c) Zone of Phyllograptus densus. 



gothian Phyllo-Tetra- (^) Zone of Isograptus gibberulus. 



graptus Beds," < Acta ^ Z()ne of PhyUoijrai) ' tns ^ ^ MS . 



Univ. Lund.,' vol. . . 



.. K lne (Jrthoceras Limestone intervenes between the last 



xxxvn, pt. 2, no. 5. 



two zones, and therefore the contrast between the faunas 

 of these zones appears to be greater than between the others. 



Before proceeding to the description of species, Tornquist suggests and 

 explains certain terms which he employs throughout this paper. 



The branch which " issues on the same side of the sicula as the first theca," 

 he calls the " primordial stipe," the other he names the " complemental stipe." 



He also distinguishes between the various parts of the first theca, and 

 designates them: (1) The "initial portion," (2) "ramifying portion," and 

 (3) " apertural portion," or true theca. 



Tornquist again points out that there has been considerable confusion in the 

 employment of the term " connecting canal," and that it can no longer be applied 

 to " that part of the complemental stipe which crosses the sicula " in Didymo- 

 graptus, etc., and he suggests the new name of " crossing canal." 



In his figures he adheres to the old method of drawing them with the apex of the 

 sicula directed downwards, though he " by no means under-rates the motives which 

 may have prevailed upon some authors to figure these fossils in a different position." 



Tornquist recognises the two genera established by Moberg as Isograptus and 

 Mseaudrograptus, though he is undecided whether to regard them as sub-genera of 

 Didymograptus or as distinct genera. 



Under the genus Dldymograptus, sensu latlori, he describes and figures : 

 Didymog. suecicus, D. patulus ( = D. hirundo), I), extensus, D. constrictus, D. balticus, 

 D. vacillans, D. filiformis, 1). flagellifer, Tullb. MS., and the new species I). 

 undulatus, D. demissus, J), geometricus, D. Holmi, D. praenuntius, D. validus, 

 D. Kurcki, and D. Mobergi. 



The genus Isograptus includes the one species 7. gibberulus, and Tornquist adds 

 a few additional notes on the structure of the initial end. 



The genus Mseandrograptas also comprises only one species: M. Schmalenseei ; 



the structure of this peculiar form is well brought out by the illustrations. 



1901 In 1901 Moberg described and figured a new species of 



Moberg, Pterograptus under the name of P. scanicus, and he compares 



" Pterogrwptus scanicue, it with Holm's species P. elegans. This species occurs 



n. sp.,' ' Geol. Foren. at F a g e lsang associated with a Glimacograptus and Didymo- 

 Forh .,' bd. 23. , 



graptus gemmus. 



